Double-Buck PFC Converter

6660IEEETRANSACTIONSONPOWERELECTRONICS,VOL.29,NO.12,DECEMBER2014

DesignandImplementationofaTransformerlessSingle-StageSingle-SwitchDouble-BuckConverterWithLowDC-linkVoltage,HighStep-Down,andConstantInputPowerFactorFeatures

YuChen,Member,IEEE,ZhihaoZhong,andYongKang

Abstract—Thispaperpresentsanewtransformerlesssingle-stagesingle-switch(S4)converterwhichintegratesabuck-typepowerfactorcorrectioncellwithabuck-typedc–dcoutputcellinaspecialway.TheproposedconverterpreservestheadvantagesofexistingtransformerlessS4converters,suchasthelowvoltagestressacrossthedc-linkcapacitor,lowcurrentstressoftheswitch,andhighstep-downinput-to-outputvoltage.Moreover,thepro-posedconverterprovidesanewattractivefeature,i.e.,itsinputpowerfactoralwayskeepsconstantevenwhentheline-andload-conditionsvary.Thesecharacteristicsmaketheproposedconvertercost-ef cient,easy-to-design,andsuitableforthelow-powerandnonisolatedapplications.Theprincipleandanalysisofthepro-posedconverterarepresentedinthispaper,andadesignexampleisalsogiventoshowthevalidityofanalysis.

IndexTerms—LEDdriver,powerelectronics,powerfactorcorrection(PFC),single-stagesingle-switch(S4)converter.

I.INTRODUCTION

M

ANYindustrialapplicationsrequirenotonlyatightdcvoltagetofeedtheirloads,butalsoahigh-inputpower

factor(PF)toreduceharmonicdistortioninthecurrentdrawnfromthegrid.Theserequirementscanbesimplysatis edbyasinglepowerfactorcorrection(PFC)converter[1]–[8].How-ever,itsoutputvoltagehasthehighripplesattwiceofthelinefrequency.Theseripplesgetevenhigherwhentheoutputvoltagebecomeslowerandtheloadbecomesheavier.TheothersolutionisusingaPFCconverterincascadewithadc–dcconverter,withwhichtheinstantaneousinputpowerandthestableoutputpowercanbedecoupledbyanintermediatedc-linkcapacitor[9]–[13].However,suchatwo-stagecon gurationsuffersfromthein-creasedcomponentcount,highcost,andcomplicatedcontrol.

ManuscriptreceivedAugust17,2013;revisedNovember3,2013andJanuary8,2014;acceptedFebruary5,2014.DateofpublicationFebruary14,2014;dateofcurrentversionAugust13,2014.ThisworkwassupportedbytheLite-OnPowerElectronicsTechnologyResearchFundunderGrant2012-04andSpe-cializedResearchFundfortheDoctoralProgramofHigherEducationunderGrant20120142120026.ThispaperwaspresentedinpartattheIEEEEnergyConversionCongressandExposition,2013.RecommendedforpublicationbyAssociateEditorT.Qian.

TheauthorsarewiththeStateKeyLaboratoryofAdvancedElectromagneticEngineeringandTechnologyandtheSchoolofElectricalandElectronicEn-gineering,HuazhongUniversityofScienceandTechnology,Wuhan430074,China(e-mail:ayu03@http://;cobeam@http://;ykang@http://).Colorversionsofoneormoreofthe guresinthispaperareavailableonlineathttp://.

DigitalObjectIdenti er10.1109/TPEL.2014.2306430

Tocompromisethesize,cost,andperformance,manysingle-stagesingle-switch(S4)convertershavebeenproposed.Fromthetopologypointofview,S4converterscanbetreatedasanintegrationversionofthetwo-stagestructure,inwhichtheswitchesinthePFCanddc–dcconverterarecombinedasone.Severaladvantagescanbeobtainedusingthisintegrationapproach:1)thePFCanddc–dccellsshareoneswitch,thesizeandcostcanbereduced;2)thehighinputPFcanbeobtainedautomaticallybythePFCcellwiththediscontinuousconductionmode(DCM),onlytheoutputvoltageneedstoberegulated,thecontrollercanbesimple;and3)theinputandoutputpowercanstillbedecoupledsincetheintermediatedc-linkcapacitorisremained,thereforethevoltageripplesintheoutputarealleviated.Duetothesefeatures,S4convertersareespeciallysuitableforthelow-powerapplicationswithcriticalsizeandcostlimitations.

S4converterswithgalvanicisolationhavebeenwellstud-iedinthepastdecades[14]–[29].However,insomelightingapplications,galvanicisolationisnotmandatorybythesafetyrequirementsorstandards.Forexample,thedriverforemergingsolid-statelightingcouldbenonisolated,astheexistingincan-descentlampsarealsonotisolatedfromthegrid[2],[30]–[32].Insuchacase,transformerlessS4convertersaremorecom-pactandcost-ef cientsolutions.Unfortunately,ifalowoutputvoltageisneeded,anextremelynarrowdutycycleisrequiredinsuchkindofconverterswithoututilizingatransformer,es-peciallyinthehigh-linecondition.Thenarrowdutycycleishardtoberealizedbyalow-costPWMcontrollerandleadstoapooref ciency[3],[33],[34].Therefore,thetopologydesignforsuchtransformerlessS4convertersshouldcompromisenotonlyagoodinputPFandastableoutputvoltage,butalsoahigh-voltagestep-downfeature(i.e.,alowoutputvoltagebutarelativelylargedutycycle).

Recently,severaltransformerlessS4convertershavebeenpresentedtomeettheaforementionedrequirements.Theboost/buck-boostS4converterispresentedin[35].TheboostPFCcellprovidesagoodinputPF,butitalsorequiresahighdc-linkvoltage,whichdegradestheconverter’sstep-downfeature.TheS4converterswithbuck-boostPFCcells[33],[34],[36]reducethedc-linkvoltage,andthevoltagestep-downcanberealizedbyabuck[34],quadraticbuck[33],orbuck-boost[36]cell.However,thesingleswitchintheaforementionedconvert-ersneedstohandlethecurrentsofbothcells,whichleadstothethermalproblemoftheswitch.In[37]and[38],abuck/

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CHENetal.:DESIGNANDIMPLEMENTATIONOFATRANSFORMERLESSSINGLE-STAGESINGLE-SWITCHDOUBLE-BUCKCONVERTER

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Fig.1.

ProposedtransformerlessS4converter.

buck-boostS4converterisproposedtofurtherreducethedc-linkvoltageandenhancethestep-downfeature,andthesingle-switchdoesnotneedtohandlethecurrentsofbothcells.How-ever,sinceitsPFCcellisbucktype,thecircuitmustbecarefullydesignedsothatasatisfactoryinputPFcanbeobtainedinthecaseoftheline-andload-conditionsvariation.

Toovercomethedrawbacksoftheaforementionedtrans-formerlessS4converterbutpreservetheiradvantages,thispaperproposesanewtopologythatintegratesabuckPFCandbuckdc–dccells,asshowninFig.1.Abuckdc–dccellisembeddedinthecircuit(thecomponentshighlightedinblue),wherethedc-linkcapacitorCbistreated …… 此处隐藏：34964字，全部文档内容请下载后查看。喜欢就下载吧 ……